Electrical trimming connector



Sept. 29, 1964 u o 3,151,309

ELECTRICAL TRIMMING CONNECTOR Filed Dec. 5, 1960 INVENTOR.

ARTHUR 6 Kan/z. arr

Asewr 3,151,309 1C6 P t nted Sept. 29, 1964 3,151,309 ELECTRHCALTRIMMING CQNNECTOR Arthur H. Kurilofi, San Diego, Calif., assignor toNon- Linear Systems Inc, Del Mar, Calif, a corporation of CaliforniaFiled Dec. 5, 19663, Ser. No. 73,652 9 Claims. (Cl. 338-269) Thisinvention relates to an electrical trimming connector and it isparticularly concerned with the trimming of the terminal end of aresistance conductor and with the securement thereof for the conductionof current, it being a general object of this invention to provide apractical connector by which the last point of contact with theconductor can be adjustably carried as circumstances require.

In electronics the exact length of a conductor is a critical factor inmany instances. For example, in a resistance winding it is necessary tocarefully trim the terminal end or ends of the conductor element and tocarefully secure said ends to electrical leads. Any deviation from therequired length of said conductor element will result in discrepanciesin the resistance afforded thereby, and one turn, more or less, cannotbe permitted. Further, the problems involved are augmented by the factthat resistance wires are very often extremely fine and delicate, andthe unit that is finally produced is therefore very small. Thus, aconnection for use with fine resistance wires and in the manufacture ofsmall sized units must be small, light-weight, and capable ofmanipulation when engaged with said wire for trimming and securement.

An object of this invention is to provide a solder connector for use intrimming and securing a resistance wire to a lead wire. Generally, thecurrent carrying capacity of the lead wire is far greater than that ofthe resistance wire and the present invention contemplates supporting orcarrying of the connector or said lead wire, said connector beingcharacterized by its bushing formation.

Another object of this invention is to provide a connector of thecharacter referred to that is selectively adjustable in order to adjustthe point of contact between the resistance wire and the connect orbushing, and to thereby selectively vary the length of said resistancewire. More particularly, the bushing is spool-shaped and such that itcan be turned and to the end that the resistance wire extendstangentially therefrom at any selected peripheral point of contact.

it is still another object of this invention to provide a connector ofthe character referred to that provides a heat-sink for the absorptionof heat when the lead wire of the finished unit is connected in acircuitry. Obviously, when heat is applied to the lead wire, even whenremote, there is the danger that said heat will be conducted via saidlead wire to enter the resistance unit and thereby to alter the same.

The various objects and features of my invention will be fullyunderstood from the following detailed description of the typicalpreferred form and application of my invention, throughout whichdescription reference is made to the accompanying drawings, in which:

FIG. 1 is a perspective view of a typical embodiment of the presentinvention and an electrical resistor. FIG. 2 is an enlarged perspectiveview of the connector or termination bushing as provided by theinvention. MG. 3 is an enlarged longitudinal sectional view of theresistor of FIG. 1 and showing the installation of a pair of terminationbushings of FIG. 2. FIG. 4 is an enlarged sectional view of the entireresistor of FIGS. 1 and 3, without the encompassing body thereof andtaken as indicated by line d-4 on FIG. 3. FIG. 5 is an end view of thestructure taken as indicated by line 55 on PEG. 4,

and FIG. 6 is an enlarged detailed sectional view taken as indicated byline 66 on FIG. 5.

The connector bushing herein disclosed is particularly useful in themanufacture of electronic components or units, such as, for example, inthe manufacture of resistors wherein a conductor of precise length isinvolved. Therefore, I will describe my invention as it is particularlyrelated to the manufacture of resistors, or the like, and in which casethe connector will be referred to specificially as a terminationbushing. It is to be understood, however, that the connector is usefulin any like situation where one electrical conductor is secured toanother for conduction of current.

in FIG. 1 of the drawings I have shown an electric component in the formof a resistor A and such as to include the termination bushing of thepresent invention, said component being shown substantially full scale.In FIG. 2 a termination bushing B is shown as it appears by itself andremoved from the structure of the resistor A. As is illustrated, theresistor A is an elongate cylindrical component having lead wires Cprojecting therefrom, and in the case illustrated there is a pair oflead wires C, each projecting oppositely on a common central axis. Inaccordance with common practice, the resistance wire D is an elongatefilament that is carried by winding it upon or around a bobbin E, saidbobbin forming the frame element of the component. The entire componentis shown as being encapsulated or molded within an encompassing body Fof epoxy material that protects it.

In FIG. 4 of the drawings I have shown the entire component less theencompassing body F, this being the stage of assembly when the connectoror connectors in the form of the termination bushing B are secured tothe wires to be joined electrically. As clearly illustrated, the twolead wires C project from opposite ends of the bobbin E, centrallythereof, and the resistance wire D is wound onto the bobbin with itsopposite terminal ends secured to a termination bushing B, respectively.In practice, the bobbin E is an elongate part formed on a central axisand it has a core N with end flanges 11 and 12 projecting radially fromthe said core. Further, it is preferred that there be a central flange13 in order to establish two separate winding areas, the flanges beingof uniform diameter. The bobbin E is made of dielectric insulatingmaterial, the two opposite lead wires C being mounted by their inner endportions that are enlarged by upsetting and which are embedded in theopposite end portions of the core Ill. In practice, the enlarged innerends of the leads C are pressed in a bore that extends through thebobbin E. With the bobbin E thus formed, the resistance wire D is woundin one direction of rotation in the area at one side of the flange l3and in the other direction at the other side of said flange. As shown inFIGS. 4 and 5 the flanges ll, 12 and 13 are slotted in order to pass theresistance wire D from and between the said winding areas.

The lead wires C, above referred to, are round in crosssection and aremade of soft metal adapted particularly to the making up of solderedconnections with other condoctors, for example of soft oxygen freecopper. The opposite ends 15 and 16 of the bobbin E are flat andparallel and normal to the axis of the lead wires C, respectively. Inaccordance with the invention, the termination bushing B is aspool-shaped element that is engaged over the lead wire C, in thisinstance there being a pair of bushings B, one adjacent the end 15 andone adjacent the end 16. As best illustrated in FIGS. 5 and 6, theresistance wire D, or filament, is connected to the lead wire C bysecurernent to the bushing B.

In accordance with the invention, the termination bushing B is ametallic part, preferably made of a soft metal of high conductivity, forexample of a free-machiningbrass. As shown, the spool-shaped bushing Bis of circular configuration and is therefore adapted tobe turned,having a drum-shaped body with end flanges 21 and 22. The body 20 iscylindrical with concentric bore 23 extending axially therethrough tofreely pass the diameter of the lead wire C. The flanges are at oppositeends of the bushing B and are flat and parallel and normal to the axisof the body 20. The said flanges 21 and 22 are as thin, in axialdimension, as is practical to machine them, they are spaced axially fromeach other a distance to accommodate several turns of resistance wire D,and they are of a diameter approximately twice that of the body 20. Atypical bushing B has a total axial extent of .040 of an inch and anoutside diameter of .070 of an inch.

In carrying out the invention the termination end portion of theresistance wire D is stripped of insulation, common to such wire, andsaid termination end portion 30 is drawn through the slot in the endflange of the bobbin E (see FIG. 5). The attachment or securement of theopposite ends of the who D can be alike, or identical, and therefore adescription of one suffices for both. In FIGS. 5 and 6 I have shown themanner in which the wire D wraps onto the body 20 and extendstangentially therefrom. The bushing B is rotatable on the lead wire Cfacilitating the wrapping of several turns of the Wire D onto thecylindrical body 20. In carrying out the invention the bared end portionof the resistance wire D is held engaged laterally against the innerface of the flange 21 or 22, this being readily accomplished manually orby lateral pressure exerted by wrapping several turns of wire D onto thebody 20, as shown. In any case, the last point of contact will beestablished at X at the periphery of the flange which is engagedlaterally by the wire D.

With the parts and relationship thereof, as above described, the lastpoint of contact X is readily adjusted relative to the length of theresistance wire D by wrapping or unwrapping the wire D on the body 2 3,with said wire engaged laterally against the flange 21 or 22, as thecase may be. For example, in fabricating precision wire-wound resistors,the last point of contact is determined by reading the total resistancefrom lead to lead with a sensitive wheatstone bridge or galvanometertype instrument. This reading is performed continuously in the trimmingoperation and the percise point for terminating is established readilyby incremental adjustment. Having made the precise adjustment desired,as measured by suitable instruments, the final and permanent securementis made by the application of a body of solder. It is preferredtherefore, that the bushing B be tin-plated and only that amount orvolume of solders is applied such as to bridge or fill between theflanges 2i and 2-2, and also between the body 20 and lead wire C. Thus,the last point of contact X is not altered by the soldering process andas a result the electrical connection is precisely accomplished withsimultaneous attachment of the bushing B in working position on the leadwire C adjacent the end of the bobbin B.

From the foregoing it will be understood how the bared end portion ofthe resistance wire is adjustably secured to an externally projectinglead wire. In practice, a relative high melting point solder can beemployed in securement of the resistance wire D to the lead wire Cthrough the termination bushing B, to the end that subsequent solderingapplied to the lead wire C when the resistor is employed in anelectronic circuit will not advertently loosen said connection. However,a feature of the bushing B is that it affords protection againstremelting of the first mentioned solder connection by establishing aheat-sink that absorbs substantial heat, thereby materially lesseningthe danger of disturbing said last point of contact X between the wire Dand bushing B.

Having described only a typical preferred form and application of myinvention, I do not wish to be limited 4i or restricted to the specificdetails herein set forth, but I wish to reserve to myself any variationsor modifications that may appear to those skilled in the art and fallwithin the scope of the following claims.

Having described my invention, I claim:

1. An electrical connector for adjustably trimming the end of a firstconductor and for securement thereof to a second conductor, andincluding, a spool-shaped bushing of electrically conductive materialand haying a bore therethrough to pass the second conductor and having acylindrical body upon which the first conductor is wrapped and having aflange to laterally engage the said first conductor to extendtangentially from a selected peripheral point of contact with saidflanges.

2. An electrical conector for adjustably trimming the end of a firstconductor and for securement thereof to a second conductor, andincluding, a spool-shaped bushing of electrically conductive materialand having a bore therethrough to pass the second conductor and having acylindrical body upon which the first conductor is wrapped and having apair of spaced end flanges to laterally engage the said first conductorto extend tangentially from a selected peripheral point of contact.

3. An electrical connector for adjustably trimming the end of a firstconductor and for securement thereof to a second conductor, andincluding, a spool-shaped bushing of electrically conductive materialand having a bore therethrough to rotatably pass the second conductorand having a cylindrical body upon which the first conductor is wrappedand having a flange to later-ally engage the said first conductor toextend tangentially from a selected peripheral point of contact withsaid flanges.

4. An electrical connector for adjustably trimming the end of a firstconductor and for securement thereof to a second conductor, andincluding, a spool-shaped bushing of electrically conductive materialand having a bore therethrough to rotatably pass the second conductorand having a cylindrical body upon which the first conductor is wrappedand having a pair of spaced end flanges to laterally engage the saidfirst conductor to extend tangentially from a selected peripheral pointof contact.

5. In combination with an electrical resistor comprising a bobbin with aprojecting lead conductor and with a resistance conductor wound on saidbobbin for trimmed connection to said lead conductor, a spool-shapedbushing of electrically conductive material rotatably engaged over saidlead conductor and upon which the said resistance conductor is Wrappedto extend tangentially from a selected peripheral point of contact.

6. in combination with an electrical resistor comprising a bobbin with aprojecting lead conductor and with a resistance conductor wound on saidbobbin for trimmed connection to said lead conductor, a spool-shapedbushing of electrically conductive material rotatably engaged over saidlead conductor and having a cylindrical body upon which the saidresistance conductor is wrapped to extend tangentially from a selectedperipheral point of contact.

7. In combination with an electrical resistor comprising a bobbin with aprojecting lead conductor and with a resistance conductor wound on saidbobbin for trimmed connection to said lead conductor, a spool-shapedbushing of electrically conductive material rotatably engaged over saidlead conductor and having a cylindrical body upon which the saidresistance conductor is wrapped and having a flange to laterally engagethe said resistance conductor to extend tangentially from a selectedperipheral point of contact with said flange.

8. In combination with an electrical resistor comprising a bobbin with aprojecting lead conductor and with a resistance conductor wound on saidbobbin for trimmed connection to said lead conductor, a spool-shapedbushing of electrically conductive material rotatably engaged over saidlead conductor and having a cylindrical body upon which the saidresistance conductor is wrapped and having a pair of spaced end flangesto laterally engage the said resistance conductor to extend tangentiallyfrom a selected peripheral point of contact with one of said flanges.

9. In combination with an electrical resistor compris- 5 ing a bobbin ofdielectric material with at least one projecting lead conductor and witha. resistance conductor wound on said bobbin for trimmed connection tosaid projecting lead conductor, a spool-shaped termination bushing ofelectrically conductive material with a 1 bore therethrough so as toengage rotatably over said lead conductor and having a cylindrical bodyupon which References Cited in the file of this patent UNITED STATESPATENTS 2,487,057 Kohring Nov. 8, 1949 2,547,405 Mitchell et a1. Apr. 3,1951 2,985,951 Solow May 30, 1961

7. IN COMBINATION WITH AN ELECTRICAL RESISTOR COMPRISING A BOBBIN WITH APROJECTING LEAD CONDUCTOR AND WITH A RESISTANCE CONDUCTOR WOUND ON SAIDBOBBIN FOR TRIMMED CONNECTION TO SAID LEAD CONDUCTOR, A SPOOL-SHAPEDBUSHING OF ELECTRICALLY CONDUCTIVE MATERIAL ROTATABLY ENGAGED OVER SAIDLEAD CONDUCTOR AND HAVING A CYLINDRICAL BODY UPON WHICH THE SAIDRESISTANCE CONDUCTOR IS WRAPPED AND HAVING A FLANGE TO LATERALLY ENGAGETHE SAID RESISTANCE CONDUCTOR TO EXTEND TANGENTIALLY FROM A SELECTEDPERIPHERAL POINT OF CONTACT WITH SAID FLANGE.